This invention relates to Computed Tomography (CT) Scanners and, more particularly, to a tomography system which can be used in a wide range of environmental conditions.
A CT scanner is a device used to generate an image of a cross-section of an object. Such devices are well known for use in the field of medicine for non-invasive diagnosis of patients. The typical CT scanner includes a rotatable disk mounted for rotation on a support frame. The disk includes a central aperture in which an object to be scanned, typically a human patient is positioned. An X-ray source is mounted to the rotatable disk and projects a beam of X-ray radiation into the object from a plurality of positions around the object. A plurality of X-ray detectors, either positioned on the rotatable disk diametrically opposite to the position of the X-ray source or positioned on the support frame at locations around the rotatable disk, produce data signals representative of the X-ray radiation that passes through the object. Using well known techniques, these data signals can be used to produce an image of a cross-section of the object which has been scanned by the system.
In at least one commercial system, the rotatable disk carries the X-ray source, typically an X-ray tube, a power supply for the X-ray tube, an array of X-ray radiation detectors, a data acquisition system (DAS), a power supply for the radiation detectors and the DAS and may carry other support systems as well. The power supplies of the commercially available scanner are electrically coupled via a power bus to a source of power provided at the support frame such as a conventional 120 or 240 volt AC power line and the DAS is electrically coupled via a data bus to a data processing system (typically a computer) for receiving data from the DAS and generating CT images. In addition, a control/status bus electrically couples the X-ray tube and the other support systems carried by the rotatable disk to control systems mounted on the support frame or peripheral to the support frame in order to permit control and status signals to be transferred. Typically, this can be accomplished either by using a power and data cable or through the use of electrically conductive slip rings in contact with electrically conductive brushes. In addition, data and control/status information can be transferred using wireless or radio frequency communications systems such as that disclosed in commonly owned U.S. Pat. No. 5,577,026, entitled APPARATUS FOR TRANSFERRING DATA TO AND FROM A MOVING DEVICE, which is hereby incorporated by reference. If a power cable is used, the disk cannot be rotated more than one revolution (360 degrees) and must be rotated back between scans. Slip rings permit the disk to rotate continuously in one direction and are therefore preferred. However, extensive wear of the slip rings and brushes results from their continuous sliding contact, thereby necessitating frequent replacement of the slip rings and/or the brushes and increasing the maintenance and operation costs of such systems. Furthermore, environmental factors, such as air-borne dust and humidity, can limit the useful life of the slip rings and brushes as well as adversely affect quality of the electrical signals and power transferred.
In addition, environmental factors, such as temperature and humidity, affect the overall operation of the CT scanning system. The X-ray radiation detectors and the electronic circuits used to process the signals generated by the detectors are sensitive to changes in temperature and humidity and must either be continuously recalibrated or compensated for with additional circuitry. The recalibration process can be time consuming and limit the amount of time the CT scanner can perform its primary function of diagnosing patients. Compensation circuitry adds to the cost and complexity of the overall system.
Accordingly, it is an object of the present invention to provide an improved CT scanning system.
Another object of the present invention is to provide an improved CT scanning system that can be operated under a wider range of environmental conditions.
And another object of the present invention is to provide an improved CT scanning system that can operate reliably and accurately under a wide range of environmental conditions.
Still another object of the present invention is to provide an improved CT scanning system that is less susceptible to environmental effects such as temperature, humidity and dust.